Apparatus for controlling a fuel injected engine driving a variable pitch propeller

ABSTRACT

By positioning a single power member, the pilot of an aircraft having a fuel injected engine and a variable pitch propeller may select a desired power level and automatically establish the engine speed, fuel flow and manifold pressure settings which will best develop the selected power. Manifold pressure is trimmed automatically in response to changes in altitude and outside temperature.

Unlted States Patent 1191 1111 3,876,329

Miller 1 1 Apr. 8, 1975 15 1 APPARATUS FOR CONTROLLING A FUEL 1536,15511/1951 Chamberlin v. 4l6/28 INJECTED ENGINE DRIVING A VARIABLE 21:32; rl umba.

exan fSO11..... PITCH PROPELLER 1796.136 6/1957 Mock 416/29 Inventor:Daniel F. Miller, Beliot, Wis.

Assignee: Woodward Governor Company,

Rockford. 111.

Filed: Aug. 31, 1973 Appl. No.: 393,311

US. Cl 416/28; 416/29 Int. Cl. B64c 11/32 Field of Search 416/29, 28,27, 30

References Cited UNITED STATES PATENTS 1,497 (1/1946 Mercier 416/291,244 9/1950 Moore 416/28 Primary Examiner-Clarence R. Gordon Atmmey.Agenl, or Firm-Wolfe, Hubbard. Leydig, Voit & Osann 157] ABSTRACT 10Claims, 4 Drawing Figures PHEHTEE AFR 81875 MAI/F010 fiiifflei VJ007/705 14/16 7167112 g Z Z 2 g Z .5 Z: W W W W M WM MW WM APPARATUS FORCONTROLLING A FUEL INJECTED ENGINE DRIVING A VARIABLE PITCH PROPELLERBACKGROUND OF THE INVENTION This invention relates to apparatus by whichthe pilot of an aircraft may control the power output of an internalcombustion engine connected to drive a variable pitch propeller. Such anengine is conventionally equipped with a governor which may be manuallyset to establish a selected engine speed and which keeps the engineturning at substantially the selected speed under varying flightconditions by adjusting the pitch of the propeller to change the load onthe engine. The engine further includes a throttle which may be manuallyadjusted to change the flow ofcombustion air to the engine. When theengine is running at a given speed and the throttle is opened manually.the pressure in the in take manifold of the engine is increased and themass flow of fuel and air to the engine also in increased to cause theengine to develop more power.

For a giv en engine to develop a given power while still operatingsafely and economically. the governor and the throttle should he set tocause the engine to run at a particular speed and a particular manifoldpressure for each different power level at which it is desired tooperate the engine. the particular values being specified by the enginemanufacturer. Thus. for each power le\el. there exists a recommendedengine speed which the pilot may establish by setting the governor andwhich remains constant regardless of changes in ambient conditions.Manifold pressure to maintain the set power. however. is dependent notonly upon the throt tle setting and engine speed but also upon thepressure of the ambient atmosphere in which the aircraft is flying.Thus. with the engine at given speed and throttle settings. manifoldpressure decreases as ambient pressure decreases when the aircraftincreases altitude. If the throttle setting is not changed to compensatefor the effects of ambient pressure. the engine will not develop powerat the desired level.

Accordingly. the engine manufacturer recommends that the throttle headjusted to establish different mani' fold pressures at differentaltitudes. When altitude is increased. the throttle is opened to pre\entthe mattifold pressure front dropping off sharply but. with pro gressiveincreases in altitude. is opened to such positions as to establishprogressively lower manifold pressures.

The engine nninufacturcr also recommends that different manifoldpressures be maintained for different ambient temperatures. Withprogressive temperature increases. the throttle should be opened toestablish progressively higher manifold pressures.

More particularly. the present invention relates to control apparatusfor fulfilling the same general purposes as the control apparatusdisclosed in Meyer U.S. application Ser. No. 329.211. filed Feb. 2. 1973and now abandoned. said application being assigned to the assignee ofthe present invention. Such apparatus simplifies the tasks of the pilotby enabling the pilot to adjust a single control member to select adesired power level and. as an incident to such adjustment. toautomatically establish the correct speed and throttle settingsneccssary to properly achieve the desired power level at any temperatureor altitude. As a result of the single control member. the pilot isrelieved of the hurden of first determining the proper speed andthrottle settings for a given power level. temperature and altitude andthen manipulating individual controls to establish these settings.

SUMMARY OF THE INVENTION The general aim ofthe present invention is toprovide new and improved single member control apparatus which issimpler in construction than prior apparatus of the same general typeand which. at the same time. more accurately establishes the propermanifold pressure.

A more detailed object is to provide novel control apparatus which setsand adjusts the throttle as a function of manifold pressure so that therecommended manifold pressures can be followed more accurately than isthe case when the throttle is adjusted to predetermined positionsestimated to produce the proper manifold pressure.

An important object of the invention is to provide unique single membercontrol apparatus which is especially suitable for use with engineshaving fuel injection systems.

A related object is to provide control apparatus in which flow of fuelto the engine is scheduled directly as a function of the position of thecontrol member. the throttle being uniquely controlled to cause mixingof the proper amount of combustion air with the fuel and to establishthe proper manifold pressure.

Another important object is to automatically reduce the flow of fuel tothe engine when the aircraft is flying at such high altitudes that themanifold pressure for obtaining the desired power level cannot bemaintained.

Still another object is to provide means with which the pilot mayoptionally select an engine speed diffen ent from the recommended speedwhile still maintaining the same power level.

These and other objects and advantages ofthe invention will become moreapparent from the following de tailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic viewschematically showing one embodiment of the new and improved controlapparatus of the present invention associated with an exemplary aircraftengine.

FIG. 2 is a family of curves which show the recommended manifoldpressures for various ambient pressures and various constant powerlevels.

FIG. 3 shows several families of curves which illustrate the recommendedrelationship between outside air temperature and manifold pressure atvarious power levels and altitudes.

FIG. 4 is a diagrammatic view showing another embodiment of the controlapparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For purposes ofillustration. the invention is shown in the drawings as embodied inapparatus for controlling a prime mover which herein is a reciprocatingpiston internal combustion engine 16 of the type commonly used in anaircraft to rotate a variable pitch propeller I7. The engine includes aconventional governor I9 which responds to changes in the engine speedbrought about by varying flight conditions such as fluctuations in airspeed and density. In response to such changes. the governor causesactuation of a hydraulic servomotor to increase or decrease thepropeller blade angle and thus adjust the load on the engine so that theload will keep the engine running at a constant desired speed at a givenhorsepower setting which is selected by the pilot to suit flightconditions.

The governor 19 includes a rotatable head 21 driven by the engine 16 andpivotally supporting flyballs 23 which are connected to a rod 24 urgeddownwardly by an adjustable speeder spring 25 and actuating a valve (notshown) for regulating the flow of pressure fluid to and from the servo20. The speed ofthe engine is maintained at a constant desired valuedetermined by the adjustment of the speeder spring. such adjustmentbeing effected by moving a speed setting control element 26 whoseposition may be adjusted manually by the pilot from inside the cockpit.A gage (not shown) is located in the cockpit to enable the pilot todeter' mine the engine speed.

in this instance. the engine 16 is equipped with a fuel injection systemwith which fuel is delivered into the individual cylinders throughinjection nozzles (not shown) communicating with fuel lines 30 which. inturn. communicate with a divider valve 31. An enginedrivcn pump 33delivers fuel to the divider valve through a line 34 at a ratedetermined primarily by the position ofa rotary metering valve 35 whichmay be adjusted manually by the pilot.

Air for supporting combustion of the fuel is admitted into the intakemanifold 36 ofthe engine [6 through an air intake unit 36a having apivoted butterfly valve 37 which constitutes the throttle of the engine.By manually opening and closing the throttle 37, the pilot may increaseand decrease the mass rate of flow of the fuelair mixture and therebyincrease and decrease the power developed by the engine. As the throttle37 is opened and closed. the pressure in the intake manifold 36increases and decreases. respectively. such pressure being reflected ona gage {not shown) in the cockpit and. when taken with engine speed andfuel flow. providing a measure of the power developed by the engine.

If the throttle 37 is at a given setting. the manifold pressure willchange when the engine speed is changed and also will change as anincident to changes in the pressure of the ambient atmosphere. That is.if engine speed is reduced. it is necessary to open the throttle andraise the manifold pressure in order to maintain the same power at thereduced speed. When ambient pressure decreases as a result of anincrease in altitude. manifold pressure will decrease unless thethrottle is opened to compensate for the decreased pressure of theatmosphere. Also. the throttle should be adjusted as the temperature ofthe ambient atmosphere changes and should be o ened to a greater degreeat higher temperatures so as to establish higher manifold pressures andprevent power from dropping off.

In order to enable the engine 16 to operate safely and with peak fueleconomy at a given power output. the engine manufacturer specifies thatthe pilot establish a particular engine speed and a particular manifoldpressure for each power level at which the pilot desires to run theengine. For one particular engine. the recommended engine speeds andmanifold pressures for each power level are shown by the curves of FIGS.2 and 3. From the curves. it will be seen that a different speed isspecified for each different power level but that each speed is ofconstant value regardless of ambient pressure and temperature. Thespecified manifold pressure. however. varies as a function of ambienttemperature and pressure since different manifold pressures are requiredto maintain the same power level at different temperatures andaltitudes. As shown by the curves. the engine manufacturer specifiesprogressively higher manifold pressures at progressively highertemperatures and specifies progressively lower manifold pressures forprogressively lower ambient pressures. the recommended manifold pressurethus drooping off as altitude is increased and ambient pressuredecreases.

With most propeller-driven aircraft, the pilot must decide upon thepower level and altitude he wishes to maintain and then consult tables.curves or the like to determine the speed and manifold pressure whichare specified for the selected power level and altitude and for thethen-existing outside temperature. The pilot then must manually setindividual controls to set the speed control element 26 and the throttle37 to the proper positions to maintain the specified speed and manifoldpressure. lf the pilot wishes to change altitude while still maintainingthe same power level. he must determine the new manifold pressure andthen re adjust the throttle to establish the new pressure. Similarly.the throttle should be adjusted if the outside temperature changes byany significant extent.

Like the control apparatus disclosed in the aboveidentified Meyerapplication. the present apparatus simplifies the tasks of the pilot byenabling him to select a desired power level simply by positioning asingle adjustable control member 40. As an incident to positioning thecontrol member 40 of the present apparatus. the speed control element 26is adjusted to establish the specified speed for the selected powerlevel and. at the same time. the throttle 37 is automatically adjustedto establish the manifold pressure which is specified for the particularpower level. altitude and temperature. If either altitude or temperaturechanges. the throttle is automatically adjusted to establish themanifold pressure at the value specified for the changed conditions.

The present invention contemplates the provision of new andcomparatively simple single member control apparatus which isparticularly adapted for use with engines [6 of the fuel injected typeand which sets the throttle 37 in such a manner as to make the actualmanifold pressure of the engine more accurately corre spond to the valuespecified by the engine manufacturer. With the present apparatus. boththe speed of the engine and the rate of fuel flow are normally scheduleddirectly as a function of the position of the control member 40.Adjustment of the control member also initiates movement of the throttleto change the manifold pressure and. in carrying out the invention. theac tual manifold pressure is sensed in order to cause the throttle to beset in a position in which the actual manifold pressure corresponds tothe specified pressure. In order that the pressure and temperature ofthe ambient atmosphere may be taken into account in establishing themanifold pressure. provision is made to sense ambient pressure andtemperature and to properly adjust the throttle for different ambientconditions.

More specifically. the control member 40 (hereinafter called the powermember) is in the form of an elongated rod whose outer end carries afixed knob 41. The inner end of the power member is pivotally connectedat 43 to the lower end of an upright lever 44 whose upper end issupported to swing about a normally fixed pivot 45. An elongated link 46is connected at its inner end to the lever 44 and is connected at itsouter end to the speed control element 26 of the governor 19. As thepower member is pushed inwardly or forwardly lie. to the right in FIG. Ithe speed control element is swung in a clockwise direction to increasethe speed setting of the governor. The ratio of the linkage between thepower member 40 and the speed control element 26 is such that movementof the power member to each of its various power level positions setsthe governor at the speed recommended for that power level. Thus. forthe present engine. movement of the power member to tis power positionestablishes a speed of ZIUO RPM. movement of the power member to its5571 power position establishes a speed of 2233 RPM and so on.

To schedule fuel flow as a function of the position of the power member40. an arm 47 is coupled to the power member 40 by a pin-and-slotconnection 49 and is connected to a fuel control element which herein isshown as being a rotatably supported shaft 50. The shaft 50 is connectedto the fuel metering valve 35 and rotates the valve as the power memberis moved inwardly and outwardly. inward movement of the power memberserving to move the valve clockwise to increase the rate of fuel flow.

In order to keep the fuel flow at the rate scheduled by the power member40. a constant pressure drop is maintained across the inlet and outletof the metering valve 35 so that the flow rate through the valve isdirectly related to the position of the valve. For this purpose. adifferential pressure valve Sl is located between the fuel pump 33 andthe fuel metering valve 35 and includes a chamber which is divided intotwo compartments 53 and 54 by a flexible diaphragm 55 carrying a valvemember 56 having spaced lands 57 and 59. Pump pressure PI is transmittedto the compartment 53 and to one end of the land 59 and is opposed by aspring 60 in the compartment 54 and by the fuel discharge pressure P2 inthe line 34. If the pump pressure Pl rises. the valve member 56 is movedto the right to cause the land 57 to open up a bypass port M and divertfuel away from the metering valve 35 and back to the fuel tank through areturn line 63. Conversely. a rise in the fuel discharge pressure P2moves the valve member to the left to close offthe bypass port 6| untilthe pump pressure Pl rises to a sufficient value to maintain the desiredconstant pressure drop across the fuel valve 35. the particular dropbeing determined by the degree of compression in the spring 60.Accordingly. when the spring 60 is set with a given compression. therate of fuel flow to the engine [6 is directly related to the positionof the fuel valve 35.

When the aircraft is taking off and climbing. it is desirable to supplyadditional fuel to the engine 16 for cooling purposes but to supply suchadditional fuel without changing the position of the fuel valve 35 asscheduled by the power member 40. This is achieved through the provisionof a mixture control member whose inner end is pivotally connected to alever 66 which. in turn. is connected to a rod 67. The spring 60 iscompressed between the rod 67 and the diaphragm 55 and thus. when therod is moved to the left. the compression in the spring is increased soas to shift the valve member 56 to the left and increase the flow offuel to the fuel metering valve 35 so that more fuel is delivered to theengine even though the position of the fuel valve is not changed.Movement of the rod 67 to the right causes the spring 60 to relax toreduce the fuel flow to the engine.

As shown. the mixture control member 65 includes two detent notches 69and 70 which coact with a spring-loaded detent 71 to hold the mixturemember in different positions. When taking off and climbing. the pilotmay push the mixture member inwardly until the detent 7] seats in thenotch 69 and. with the mixture member in this position. the differentialpressure valve 51 is set to deliver the desired additional fuel to theengine. After cruising altitude has been reached, the mixture member maybe pulled outwardly to seat the detent in the notch 70 and set thedifferential pressure valve 51 to establish the proper pressure drop forcruising solely under the control of the power member 40.

By pulling the mixture member 40 outwardly sufficiently far to seat thedetent 71 in a third notch 73. the pilot may shift the valve member 56to the extreme right to cause the land 57 to fully open the bypass port61 and the land 59 to fully close the passage leading to the fuel valve35 and thereby cut off the flow of fuel to the engine 16 and unload thepump 33. As the mixture lever is pulled outwardly to its cut-offposition. a button 75 on the end of the rod 67 engages an extension 76on the diaphragm 55 and shifts the valve member 56 to the right.

Movement of the throttle 37 is effected by a throttle servo 80 having apiston 81 slidable in a cylinder 83 and connected to the throttle bymeans of a pivoted linkage 84. As pressure fluid is admitted into theleft end of the cylinder through a line 85. the piston 81 is shifted tothe right to open the throttle. When pressure fluid is dumped from theleft end of the cylinder. a spring 86 shifts the piston to the left toclose the throttle.

The throttle servo 80 is controlled by a pilot valve 87 having a valvespool 89 which is adapted to slide downwardly within a bore 90 toconnect the servo line 85 with a line 9l leading to a source of pressurefluid such as the pump 33. With the valve spool 89 in its downwardposition. fuel under pressure is delivered to the throttle servo 80 toopen the throttle 37. When the valve spool is shifted upwardly from theposition shown in FIG. I. the servo line 85 communicates with a drainline 93 and thus the throttle piston 81 may return to the left to closethe throttle.

ln keeping with the invention. movement of the power member 40 to aselected power level position serves to adjust the pilot valve 87 tochange the setting of the throttle 37 and establish the manifoldpressure which is specified for the selected power level. the throttlebeing moved until the actual manifold pressure corresponds to thepressure dictated by the position of the power member and by ambientpressure and temperature. For these purposes. the arm 47 carries athrottle control element in the form of a cam 94 which rides against aroller follower 95 located at the upper end of a compression spring 96whose lever end bears against the upper end of the spool 89 of the pilotvalve 87. As the power member 40 is pushed inwardly to in crease power.the cam 94 is rocked clockwise and acts through the follower 95 and thespring 96 to shift the valve spool 89 downwardly and cause opening ofthe throttle to increase the manifold pressure. The cam is shaped toschedule the manifold pressure at values which are properly correlatedwith the engine speeds ttahlished at different positions of the powermember 0. As the cam is adjusted. at pressure signal is transmit- :dfrom the intake manifold 36 to the pilot valve 87 to ause the throttleto assume a position establishing the etual manifold pressure at a valuewhich corresponds v the commanded value.

To transmit the manifold pressure signal. a line 97 :ads from themanifold 36 to a chamber 99 which ouses an evacuated bellows 100connected to the user end of the valve spool 89 and sealed from the alvebore 90 by a second bellows 101. the latter com iunicating with thedrain line 93 through a passage 03 in the valve spool and being filledwith fuel at drain ressure. As manifold pressure increases and reases.the bellow I00 contracts and expands. respecvely. to shift the valvespool 89 upwardly and downardly. Accordingly. as the cam 94 is adjustedto shift 1e valve spool downwardly and open the throttle. the ianifoldpressure increases and acts through the beliws 100 to cvert aprogressbely increasing upward \rce on the valve spool. When themanifold pressure icreases to a sufficient value that the upward forceex rted on the lower end of the spool balances the downard force e\ertedon the upper end of the spool. the itter ts moved to its centeredposition shown in FIG. and the throttle 37 is stopped in a position inwhich :ie actual manifold pressure coincides \\ith the comiandedpressure. l hus. movement of the power memer 40 does not cause thethrottle to move to a particuir predetermined position but insteadcauses the throtlc to move until the commanded manifold pressure isctually established. Asa result. the manifold pressure pecified for agiven power level can be accurately set nd maintained.

lf the cam 94 is in a given position and the altitude f the aircraft isincreased. the manifold pressure dereases as a result of the decreasedpressure of the air t the higher altitude. As the manifold pressure dcreases. the bellows I00 evpands and shifts the valve pool 89 downwardlyto cause opening of the throttle B7 to obtain the proper manifoldpressure. in order to chieve the recommended manifold pressure at theiigher altitude. however. the throttle should not open o far as to bringthe manifold pressure back up to its iriginal value. Instead. thethrottle should open to a poition establishing a manifold pressureslightly lower han that maintained at the lower altitude. in otherrords. the throttle should be positioned to cause maniold pressure todroop at higher altitudes as indicated w the curves shown in FIG. 2. inorder to provide such lroop. a bellows 105 which is open to theatmosphere s attached to the upper end portion of the valve spool l9 andis surrounded by a chamber I06 communicating vith the drain line 93through the passage 103 and illed with fuel at drain pressure. Thebellows 101 and 05 serve to seal the ends ofthe valve bore 90 and bothire of equal area so that internal fuel pressure changes lave no effecton the position of the valve spool 89.

As the altitude of the aircraft increases and the presure and density ofthe ambient atmosphere decrease. he bellows )5 tends to contract toraise the valve pool 89. As manifold pressure decreases the bellows .00tends to lower the valve spool to restore the maniold pressure to itsoriginal value but. because of the imbient pressure bias applied by thebellows 105, the nanifold pressure droops and actually takes on a valuelightly lower than its original value. The bellows 105 is of smallerarea than the bellow I00 and the effect of ambient pressure on manifoldpressure is proportional to the ratio of the areas. By properly sizingthe bellows I00 and I05. the manifold pressure may be made to droopsubstantially in accordance with the curves of FIG. 2.

To adjust the manifold pressure automatically in response to changes inoutside temperature. a cantilevered bimetallic strip I07 is shown asbeing sandwiched between the compression spring 96 and the upper end ofthe valve spool 89. As temperature increases, the bimetallic stripflexes downwardly and applies a downward bias to the valve spool so asto open the throttle 37 and cause the manifold pressure to increasesubstantially in accordance with the curv es shown in FIG. 3. Iftemperature decreases. the bimetallic strip flexes upwardly and reducesthe spring pressure on the valve spool 89. The throttle thus closes tolower the manifold pressure.

From the foregoing. it will be apparent that the pres ent inventionbrings to the art new and improved control apparatus in which a singlepower member 40 schedules speed and fuel flow directly as a function ofthe position in which the power member is set. The power member alsoschedules manifold pressure in accordance with speed and fuel flow whilethe bias applied by the pressure and temperature sensors I05 and 107scrv es to trim the manifold pressure so as to establish the latter atthe values specified for various altitudes and temperatures.Accordingly. the pilot may select a desired power level simply bysetting the power member and. as an incident to such positioning. speed.fuel flow and manifold pressure are automatically and accurately set atthe values which are recommended by the engine manufacturer to developthe desired power at a given altitude and with a given temperature.

lf the power member 40 of the engine [6 is set for a given power leveland the aircraft is flying at an altitude which lies to the right of thediagonal line (1 shown in FIG. 2. the atmospheric pressure is so lowthat the manifold pressure needed to maintain the desired power settingcannot be obtained even if the throttle 37 is fully opened. Lnder thesecircumstances. it is desirable to reduce the fuel flow to a rate belowthat scheduled b the position of the power member so that the actualfuel flow will be correlated with the reduced power which is actuallyobtained. Such reduction in fuel flow if advantageously achieved bybypassing some of the fuel in the engine line 34 to the drain line 93 byway of a line 108 communicating between the line 34 and a port 109 inthe pilot valve 87. the port normally being closed by a land 109a on thevalve spool 89. [f the atmospheric pressure is so low that the manifoldpressure commanded by the position of the power member and by theoutside temperature cannot be obtained. the valve spool 89 will shiftdownwardly to uncover the port I09 and allow some of the fuel to bypassthe engine l6 and flow to the drain line 93. the extent of downwarddisplacement of the spool being proportional to the difference betweenthe commanded manf fold pressure and the actual manifold pressure. As aresult. even when the selected power setting cannot be obtained. a fuelmixture ofthe correct fuel/air ratio will be delivered to the engine toavoid the wasting of fuel and to keep the engine operating under safeconditions. The bypass of the scheduled fuel also will occur duringthrottle bursts. some fuel being bled to drain until the manifoldpressure reaches the new setting.

Means are provided to enable the pilot to trim the engine speedindependently of the position of the power member 40 so that the pilotmay maintain a given power while running the engine 16 at a speed of hisown selection in order to achieve lowest noise conditions. best fueleconomy and the like. Herein. these means comprise a manually adjustablespeed trim member I I whose inner end is connected to the upper endofthe lever 44 by the pivot 45. Normally. the speed trim member H0 isheld in a cruise position shown in FIG. I by a spring-loaded detent IIIwhich seats in a notch 113 in the speed member. With the speed member110 in the cruise position. the speed of the engine 16 is established inaccordance with the position of the power member 40 and is scheduledwith respect to power as shown by the can es of FIGS. 2 and 3. If thepilot wishes to develop the same power while running the engine ateither a slightly faster or slightly slower speed. he may adjust thespeed member 110 inwardly or outwardly. As an incident to suchadjustment. the lever 44 is rocked about the lower pivot 43 an actsthrough the link 46 to change the setting of the speed control element26 of the governor I).

When the speed ofthe engine 16 is trimmed. it is necessary to alsoadjust the manifold pressure in order to maintain the power called forby the position of the power member 40. For this purpose. a pivotedbellcrank H4 is connected between the speed trim memher I Ill and theupper end of an upright link 115 whose lower end is connected to a lever[[6 adapted to swing upwardly and downwardly about a fixed pivot H7. Thebimetallic strip 107 is cantilevered on the inner end portion of thelever llfi and thus the force exerted on the upper end of the alve spool89 by the compression spring 96 may be adjusted by swinging the leverupwardly and downwardly. If the pilot moves the speed member 110inwardly to establish a speed slightly higher than dictated by the powermember 40. the \al\c spool 89 is lifted to cause closing of the throttle37 and lowering of the manifold pressure. Conversely. lowering of thespeed by the speed trim member Ill) results in the valve spool beingshifted downwardly to cause an increase in manifold pressure. Thus. withthis arrangement. the manifold pressure is adjusted at the same timeengine speed is trimmed so that the engine still will de\elop the powerspecified by the setting of the power member 40.

'l he peed trim member also is used to enable the pilot to override thepilot valve 87 and manually control the throttle 37 in a direct mannerif the bellows 100 and I should malfunction or if some other failureshould occur in the control apparatus. As shown. a fin ger 120 iscarried on the inner end ofthe lever I16 and underlies the upper end ofthe valve spool 89. When the pilot pushes the speed member [l0 inwardlysufficicntly far to seat the detent 111 into an override notch I21. thefinger 120 is swung upwardly and lifts the valve spool 89 so as to portthe left side of the throttle servo 80 to drain. Under this condition.the spring 86 shifts the throttle piston 8| to the left until thethrottle linkage 84 stops against a screw I23. The latter is adjustablythreaded into a plate 124 connected to an arm I which. in turn. iscarried on the shaft 50. When the pilot valve 87 is overridden. thepilot may directly move the throttle 37 by adjusting the power member toturn the shaft 50 and cause the screw 123 to shift the throttle linkage84 and change the throttle setting. In order to permit the throttle tobe opened under direct manual control. the linkage 84 is attached to thethrot' tle piston 81 by a yieldable connection indicated generally bythe reference numeral 126 and having a spring 126a enabling the linkageto move relative to the piston when manually adjusted. the spring 1261:also serving to bias the linkage against the screw 123. The adjustedposition of the screw [23 determines the position of the throttle 37 atidle speed while fuel flow to the engine 16 at idle speed is determinedby the position of a second adjustable screw 127 adapted to engage theplate 124 and limit the extent to which the power member 40 may bepulled outwardly.

Another embodiment ofa control apparatus is shown in FIG. 4 in whichparts corresponding to those of the first embodiment are indicated bythe same but primed reference numerals. In this instance. the member110' is not used to trim the speed of the engine 16' during flight butinstead is used to purge the prop servo 20' of cold oil when the engineis first started on the ground during cold weather. By pulling outwardlyon the member 110' against the bias ofa spring [30. the speed setting ofthe governor l9 maybe reduced to such a value that all of the cold oilin the prop servo is dumped therefrom through the governor valveassociated with the rod 24'. The member Ill) then may be releasedinwardly to its position shown in FIG. 4 so as to increase the speedsetting of the governor l6 and deliver warm oil to the prop servo 20'.It will be noted that movcment of the member 110 has no effect on theposition of the pilot valve spool 89' since the control apparatus shownin FIG. 4 does not include a linkage correspond ing to the linkage 14.H5 and H6 ofthe control apparatus shown in FIG. 1. Accordingly. themember 110' may change the speed setting ofthe governor 16' withoutchanging the setting of the pilot valve spool 89'.

Like the control apparatus of the first embodiment. the controlapparatus shown in FIG. 4 includes a mixture control member which may beused to cut off the fuel flow and to richen or lean the fuel-air mixturemanually. The mixture control member 65. however. is moved from itsnormal cruise position shown in FIG. 4 only when special conditionsdictate that the fuel-air mixture should be made richer or leaner.During take off and climb. an enrichment orifice 131 in the meteringvalve 35' automatically richens up the mixture to provide for additionalcooling of the engine. Accordingly. it is not necessary to move themixture control member 65' during normal take off and climb.

In the control apparatus shown in FIG. 4. the bellows [00' is locateddirectly in the manifold 36' and is filled with a gas such as helium.When the temperature of the air in the manifold 36' increases. the gasexpands the bellows I00 to shift the pilot valve spool 89' downwardlyand cause the throttle 37' to open and increase the manifold pressure.The bellows thus is responsive not only to the pressure but also thetemperature of the air in the manifold so as to provide a comparativelyaccurate reflection of the temperature of the air entering the cylindersof the engine 16'.

A further difference between the control apparatus shown in FIG. I andthat shown in FIG. 4 resides in the manner of positioning the throttle37'. In the control apparatus shown in FIG. 4, the throttle is setdirectly by the power lever 40' and then is trimmed by the throttleaervo 80' in accordance with manifold pressure. ambirnt pressure andtemperature. As shown. a linkage 140 s connected directly to the shaft50' and also is coniected at l4! to a differential lever 143. The latteris )ivoted intermediate its ends at I44 and is connected it its lowerend to a linkage 145 which is connected to ;he throttle 37. When theshaft 50' is rotated clock ivise by inward movement of the power member40'. lhL linkages I40 and 145 and the lever H3 cause the :hrottle toopen.

If the position of the throttle 37' as set by the shaft 50 does notestablish the manifold pressure comnanded by the cam 94' and by ambientpressure and :emperature. the pilot valve spool 89 is displaced and:auses the throttle servo 80 to adjust or trim the throtile until thecommanded manifold pressure is reached. For this purpose. a link 146 isconnected to the servo piston 8| and its outer end defines theintermediate pi\ot 144 for the differential lever [43. When the pis ton8| is shifted by displacement of the valve spool 89'. the link 146causes the lever [43 to swing about the upper pivot 141 and adjust thethrottle until the actual manifold pressure corresponds with thecommanded value.

I claim as my invention:

1. Control apparatus for an internal combustion engine connected todrive a variable pitch propeller. said engine having:

a. a governor adjustable to different speed settings and operable tovary the pitch of the propeller to maintain the actual speed of theengine substantially in agreement with a set speed.

b. a fuel valve adjustable to different positions to regulate the rateof flow of fuel to the engine, and

c. a throttle adapted to be set in different positions to regulate theflow of combustion air to the engine and to adjust the manifold pressureof the engine.

said control apparatus including:

a. a speed control element which is operable when moved to change thespeed setting of said governor.

b, a fuel control element which is operable when moved to change theposition of said fuel valve. and

c. a throttle control element which is movable to different positions.

said control apparatus further including:

a. a control member connected to all three of said elements and operableto move all three elements in response to being manually adjusted,thereby to correlate the speed of said engine with the rate of fuel flowand to set said throttle control element in a position correlated bothwith engine speed and rate of fuel flow.

b. first means for sensing variations in the density of the ambientatmosphere.

c. second means for sensing variations in the manifold pressure of saidengine.

d. third means responsive to said first and second means and to theposition of said throttle control element and operable to automaticallymove said throttle in response to variations in the density of theambient atmosphere and/or the manifold pressure ofsaid engine and/or inresponse to movement of said throttle control element and operable tolocate said throttle in a position causing the manifold pressure to becorrelated with the density of the ambient atmosphere and the positionof the throttle control element. and

. means causing said fuel to flow past said fuel valve with apredetermined constant pressure drop whereby the flow rate of said fuelpast said valve is directly proportional to the position of said valve.said last-mentioned means being selectively adjust able to cause saidfuel to flow past said valve with a different constant pressure dropwhereby the flow rate of the fuel may be changed without changing theposition of said valve. and a second control member connected to saidlast-mentioned means and operable to adjust the latter in response tobeing manually moved.

2. Control apparatus as defined in claim 1 in which said first meansincludes pressure-responsive means for sensing variations in thepressure of the ambient atmosphere.

3. Control apparatus as defined in claim 2 in which saidprcssure'responsive means cause said throttle to close when the densityof the ambient atmosphere decreases as a result of a decrease in thepressure of the ambient atmosphere and in which said second means causesaid throttle to open when manifold pressure decreases as a result of adecrease in the pressure of the ambient atmosphere. saidpressureresponsive means and said second means being correlated with oneanother so the resultant effect of a given decrease in ambient pressurecauses opening of said throttle but by a lesser amount than would be thecase in the absence of said pressureresponsive means.

4. Control apparatus as defined in claim 1 in which said first meansincludes temperature-responsive means for sensing variations in thetemperature of the ambient atmosphere and for causing said throttle toopen when the temperature ofthe ambient atmosphere increases.

5. Control apparatus as defined in claim I in which said first meansincludes pressure-responsive means for sensing variations in thepressure of the ambient atmosphere and further includestemperature-responsive means for sensing variations in the temperatureof the ambient atmosphere.

6. Control apparatus for an internal combustion engine connected todrive a variable pitch propeller. said engine having:

a. a governor adjustable to different speed settings and operable tovary the pitch of the propeller to maintain the actual speed of theengine substantially in agreement with a set speed.

b. a fuel valve adjustable to different positions to regulate the rateof flow of fuel to the engine. and

c. a throttle adapted to be set in different positions to regulate theflow of combustion air to the engine and to adjust the manifold pressureof the engine.

said control apparatus including:

a. a speed control element which is operable when moved to change thespeed setting of said gover nor.

b. a fuel control element which is operable when moved to change theposition of said fuel valve. and

c. a throttle control element which is movable to different positions.

said control apparatus further including:

a. a control member connected to all three of said elements and operableto move all three elements in iii response to being manually adjusted.thereby to correlate the speed of said engine with the rate of fuel flowand to set said throttle control element in a position correlated bothwith engine speed and rate of fuel flow.

b. first means for sensing variations in the density of the ambientatmosphere.

c. second means for sensing variations in the manifold pressure of saidengine.

d. third means responsive to said first and second means and to theposition of said throttle control element and operable to automaticallymove said throttle in response to variations in the density of theambient atmosphere and/or the manifold pressure of said engine and/or inresponse to movement of said throttle control element and operable tolocate said throttle in a position causing the manifold pressure to becorrelated with the density of the ambient atmosphere and the positionof the throttle control element. and

e. means for automatically bypassing fuel away from said engine whenmanifold pressure drops to a predetermined level.

7. Control apparatus for an internal combustion engine connected todrive a variable pitch propeller. said engine having:

a. a governor adjustable to different speed settings and operable tovary the pitch of the propeller to maintain the actual speed of theengine substantially in agreement with a set speed.

b. a fuel valve adjustable to different positions to regulate the rateof flow of fuel to the engine. and

c. a throttle adapted to be set in different positions to regulate theflow of combustion air to the engine and to adjust the manifold pressureof the engine.

said control apparatus including:

a. a speed control element which is operable when moved to change thespeed setting of said governor.

b. a fuel control element which is operable when moved to change theposition of said fuel valve. and

c. a throttle control element which is movable to different positions.

said control apparatus further including:

a. a control member connected to all three of said elements and operableto move all three elements in response to being manually adjusted.thereby to correlate the speed of said engine with the rate of fuel flowand to set said throttle control element in a position correlated bothwith engine speed and rate of fuel flow.

b. first means for sensing variations in the density of the ambientatmosphere.

c. second means for sensing variations in the manifold pressure of saidengine.

d. third means responsive to said first and second means and to theposition of said throttle control element and operable to automaticallymove said throttle in response to variations in the density of theambient atmosphere and/or the manifold pressure of said engine and/or inresponse to movement of said throttle control element and operable to 10cate said throttle in a position causing the manifold pressure to becorrelated with the density of the ambient atmosphere and the positionof the throt tle control element. and

e. a second control member connected to said speed control element andoperable when adjusted manually to move said speed control elementwithout moving said fuel control element whereby engine speed may bechanged without changing the rate of fuel flow. and means responsive tomovement of said second control member and coacting with said thirdmeans to adjust the position of said throttle when said second controlmember is moved.

8. Control apparatus as defined in claim 7 further including meansconnected to said second control member and operable to disable saidthird means when said second control member is moved to a predeterminedposition.

9. Control apparatus as defined by claim 8 further including meansmovable by said first control member and operable to move said throttlewhen said third means are disabled and said first control member ismoved.

10. Control apparatus as defined in claim 7 further including meanscausing said fuel to flow past said fuel valve with a predeterminedconstant pressure drop whereby the flow rate of said fuel is directlyproportional to the position of said valve. said lastmentioned meansbeing selectively adjustable to cause said fuel to flow past said valvewith a different constant pressure drop whereby the flow rate of thefuel may be changed without changing the position of said valve. and athird control member connected to said last mentioned means and operableto adjust the latter in response to being manually moved.

1. Control apparatus for an internal combustion engine connected todrive a variable pitch propeller, said engine having: a. a governoradjustable to different speed settings and operable to vary the pitch ofthe propeller to maintain the actual speed of the engine substantiallyin agreement with a set speed, b. a fuel valve adjustable to differentpositions to regulate the rate of flow of fuel to the engine, and c. athrottle adapted to be set in different positions to regulate the flowof combustion air to the engine and to adjust the manifold pressure ofthe engine,
 2. Control apparatus as defined in claim 1 in which saidfirst means includes pressure-responsive means for sensing variations inthe pressure of the ambient atmosphere.
 3. Control apparatus as definedin claim 2 in which said pressure-responsive means cause said throttleto close when the density of the ambient atmosphere decreases as aresult of a decrease in the pressure of the ambient atmosphere and inwhich said second means cause said throttle to open when manifoldpressure decreases as a result of a decrease in the pressure of theambient atmosphere, said pressure-responsive means and said second meansbeing correlated with one another so the resultant effect of a givendecrease in ambient pressure causes opening of said throttle but by alesser amount than would be the case in the absence of saidpressureresponsive means.
 4. Control apparatus as defined in claim 1 inwhich said first means includes temperature-responsive means for sensingvariations in the temperature of the ambient atmosphere and for causingsaid throttle to open when the temperature of the ambient atmosphereincreases.
 5. Control apparatus as defined in claim 1 in which saidfirst means includes pressure-responsive means for sensing variations inthe pressure of the ambient atmosphere and further includestemperature-responsive means for sensing variations in the temperatureof the ambient atmosphere.
 6. Control apparatus for an internalcombustion engine connected to drive a variable pitch propeller, saidengine having: a. a governor adjustable to different speed settings andoperable to vary the pitch of the propeller to maintain the actual speedof the engine substantially in agreement with a set speed, b. a fuelvalve adjustable to different positions to regulate the rate of flow offuel to the engine, and c. a throttle adapted to be set in differentpositions to regulate the flow of combustion air to the engine and toadjust the manifold pressure of the engine,
 7. Control apparatus for aninternal combustion engine connected to drive a variable pitchpropeller, said engine having: a. a governor adjustable to differentspeed settings and operable to vary the pitch of the propeller tomaintain the actual speed of the engine substantially in agreement witha set speed, b. a fuel valve adjustable to different positions toregulate the rate of flow of fuel to the engine, and c. a throttleadapted to be set in different positions to regulate the flow ofcombustion air to the engine and to adjust the manifold pressure of theengine,
 8. Control apparatus as defined in claim 7 further includingmeans connected to said second control member and operable to disablesaid third means when said second control member is moved to apredetermined position.
 9. Control apparatus as defined by claim 8further including means movable by said first control member andoperable to move said throttle when said third means are disabled andsaid first control member is moved.
 10. Control apparatus as defined inclaim 7 further including means causing said fuel to flow past said fuelvalve with a predetermined constant pressure drop whereby the flow rateof said fuel is directly proportional to the position of said valve,said lastmentioned means being selectively adjustable to cause said fuelto flow past said valve with a different constant pressure drop wherebythe flow rate of the fuel may be changed without changing the positionof said valve, and a third control member connected to saidlastmentioned means and operable to adjust the latter in response tobeing manually moved.